Vehicle drivers have over the last decades been assisted by GPS navigation. GPS navigation provides navigation data which can be superposed on a map and readily simplifies the maneuvering in otherwise uncharted territories for the driver. With the introduction of autonomous vehicles, the demand for improved navigation data as well as improved additional navigation systems has increased. Just as a matter of example, the GPS signal is not always available. In urban environment for example, the GPS signal may be blocked by high buildings.
Additional navigation data can be collected using road side lines and center lines, sometimes also referred to as road lane markings. Cameras may be used to detect and track the position of the vehicle with respect to the closest road side line for example. Navigating using the road side lines has its drawbacks however. Snow and dirt may cover the road side lines, making them more difficult to detect. In some sections of a road, the road side lines may be worn down to such an extent that they are nearly impossible to detect.
Landmark navigation is a navigation method in which landmarks are used to identify the position of the vehicle. The US patent application Ser. No. US 2014/0163878 A1 disclose an in-vehicle navigation apparatus which comprises a landmark information acquiring unit. The system further includes a lane guide unit. The apparatus assists in determining the appropriate lane in which the user should drive. The landmark information acquiring unit acquires landmark information representing an object which serves as a landmark. The lane at which the vehicle is permitted to travel is restricted at the specific point, defined by the landmark. The landmark functions as a trigger and basically; a driver receiving the guidance is capable of appropriately performing the driving operation to change to the guided lane by using the confirmation of the object existing along the route as a trigger event.
The above mentioned in-vehicle navigation apparatus suffer from some drawbacks however. The in-vehicle navigation apparatus does not provide navigation data which is reliable enough for autonomous driving. Further, the system appears to be limited to the selection of lanes.
It appears that there is a need for improved navigation units and methods for gathering navigation data.